Lubricating grease

ABSTRACT

LUBRICATIING GREASES ARE IMPROVED AS TO BLEEDING, WATER WASH-OUT, AND WHEEL BEARING LEAKAGE PROPERTIES BY THE ADDITION OF A HYDROGENATED BUTADIENE-STYRENE COPOLYMER.

United States Patent Olfice p 3,728,261 Patented Apr. 17, 1973 ABSTRACT OF THE DISCLOSURE Lubricating greases are improved as to bleeding, water wash-out, and wheel bearing leakage properties by the addition of a hydrogenated butadiene-styrene copolymer.

This invention relates to improved lubricating greases. In accordance with another aspect, this invention relates to the addition of hydrogenated butadiene-styrene copolymers to grease formulations to improve bleeding, water wash-out, and wheel bearing leakage properties of the lubricating grease. In accordance with a further aspect, this invention relates to alkali metal soap greases optionally containing a polyolefin having improved characteristics, especially with respect to bleeding, water washout, and wheel bearing leakage, by adding thereto a small amount of a hydrogenated butadiene-styrene copolymer having defined amounts of butadiene and styrene.

Various efforts have been made wtih respect to improving the physical characteristics of lubricating greases. One problem often encountered with known greases is bleeding during use, including wheel bearing leakage. Also, loss of grease due to water wash-out is a problem of great concern with automobile greases. In accordance with the invention, it has been found that addition of a hydrogenated butadiene-styrene copolymer to grease compositions substantially improves the grease with respect to bleeding, water wash-out, and wheel bearing leakage properties.

Accordingly, an object of this invention is to provide an improved lubricating grease.

A further object of this invention is to provide a lubricating grease which is improved in bleeding, water washout, and wheel bearing leakage properties.

Other objects and aspects, as well as the several advantages of the invention, will be apparent to those skilled in the art upon reading the specification and the appended claims.

In accordance with the invention, a lubricating grease is improved in its physical properties, especially with respect to bleeding, water washout, and wheel bearing leakage, by the addition of a hydrogenated butadienestyrene copolymer.

More specifically in accordance with the invention, a highly hydrogenated butadiene-styrene copolymer is added to automotive grease formulations to prevent bleeding, water Wash-out, and wheel bearing leakage while maintaining desirable properties.

The invention is particularly adaptable for improving alkali metal soap greases containing minor amounts of polyole'fin whereby the grease formulation is improved in physical characteristics by addition of the hydrogenated butadiene-styrene copolymer.

The hydrogenated copolymers of the present invention have a molecular Weight in the approximate range of about 10,000 to about 200,000, a now preferred range being from about 20,000 to about 100,000. The copolymers can be one containing from 30 to about 75 parts by weight of butadiene per 100 parts by weight of monomers. Thus, the broad range of the butadiene-styrene rati in the copolymer can extend from about 30:70 to about 75:25.

7 Claims The hydrogenated copolymer molecular weight referred to throughout this application refers to numberaverage molecular weight. The number-average molecular weight of a specific butadiene-styrene copolymer is determined by methods which are conventional in the art. For example, a particularly convenient method for determining the molecular weight of copolymers in the 15,000 to 200,000 range is by the membrane osmometer. Such a procedure is described in a. paper by R. E. Steele et al. at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy in March 1963. For copolymers in the 5,000 to 15,000 range, ebullioscopic methods are appropriate, such as the technique described by R. L. Arnett et al. in the Journal of Polymer Science, Part A, vol. I, pp. 2753-2764 (11963). For copolyrners having molecular weights below 5,000, methods employing the use of a vapor pressure osmometer such as that available from Mechrolab Inc., 1062 Linda Vista Ave., Mountain View, Calif, are appropriate.

The hydrogenated copolymers of the present invention can be prepared by any of the conventional techniques known in the art. For example, the butadiene-styrene mixture of monomers can be polymerized using butyllithium as the catalyst. The hydrogenation can be carried out over a nickel octoatetriethylaluminum catalyst system. US. Pat. 2,864,809, R. V. Jones et al., issued Dec. 16, 1958, describes a technique for hydrogenating butadiene-containing polymers. The hydrogenated butadienestyrene copolymers of the present invention are polymers which have been sufiiciently hydrogenated to remove substantially all of the olefinic unsaturation leaving only the aromatic unsaturation.

The additive, copolymer of the present invention is generally added to the lubricating grease in amounts which range from about 0.5 to about 10 weight percent of the lubricating grease, preferably 1 to '5 weight percent.

Generally, any conventional and commercially available grease is amenable to this invention. The grease employed can have been thickened in any known manner such as by the use of soaps and/or by dissolving polymers in the oil at temperatures of at least 245 F. and the like.

Suitable greases include substantially any grade of ilowable grease as defined by the National Lubricating Grease Institute (NLGI). For example, NLGI grade greases from 000 to 6 can be employed in this invention. Also, greases having an ASTM D 217-68 penetration at '60 strokes in the range of to 475 can be employed.

The lubricating oil bases which can be employed to make greases of this invention can be mineral, vegetable, or animal in nature, preferable lubricant bases having at least a major amount of mineral origin. Such oils include refined oils having a viscosity of from about '35 to about 240 SUS as 210 F. White mineral oil is Well as other specialty oils can be used and are among the preferred oils.

Thickeners for the oils can be employed in amounts up to 20 weight percent of the oil. Various soaps normally used to thicken greases can be used and they include metal salts of high molecular weight acids, for example, acids of '10 to 30 and preferably 16 to 24 carbon atoms, either synthetic or of animal or vegetable origin. Other carboxylic acids useful for making soaps of metal salts include those derived from 'tallows, hydrogenated fish oil, castor oil, wool grease, and rosin. Generally the alkali metal or alkaline earth metal or aluminum or lead salts of acids such as lauric, palmitic, oleic, stearic, and the like are used. One of the preferred soaps is the lithium soap of 12-hydroxystearic acid. While soaps of a general nature can be used in the greases of this invention, it

should be understood that the invention is of use with soapless greases formed essentially from polymers and oil alone, with or without small amounts of additives such as rust inhibitors, antioxidants, fillers, and the like. Thus, polymers such as polyethylene and polypropylene can be employed as thickeners, together, alone, or in conjunction with other thickeners such as soap.

EXAMPLE I A butadiene-styrene copolymer according to the invenion was compared with a number of other known grease additives. The grease employed was an automotive (Philube ASM, Product of Phillips Petroleum Company, Bartlesville, Okla.) grease containing 1 percent polyethylene. The amount of each additive was 2 percent based upon total grease. Results of these tests are set forth below.

Penetrations 1 Wheel bearing Norma H011- 7 Drop 9 ASTM Water leakage," gms. man 3 psi. 60 10,000 point, bleed; washout} drop 3 in 264 Unworked strokes strokes F. percent percent 260 F. 325 F. hrs.

ASM grease 264 264 268 371 2. 78 3. 75 4. Plus 2% Paratone N (polyisobutylene) 257 260 274 377 1.37 0 8. 4 3. 55 Plus 2% Acryloid 909 (methacrylate) 221 248 263 385 2. 10 1. 25 8. 6 3. 85 41. 0 Plus 2% butadiene-styrene copolymer (40% butadiene and 60% styrene)- 264 264 278 382 0 0 1. 8 3. 35 5. 0

1 ASIM D-217-68. 1 AS'IM D566-64. ASTM D1742-64. 4 AS'IM D12fi4-63. ASTM D1263-61. ASTM D942-58.

Other materials normally used 111 greases can also be 25 In the above tests all of the V1. improvers improved employed in the greases applicable to this invention. For example, additives such as rust inhibitors, antioxidants, fillers, pigments, perfumes, and the like can be employed. Some examples of such materials include propylenediamine, phenyl a naphthylamine, phenothiazine, mica, asbestos, powdered lead, powdered zinc, talc, alumina, titanium dioxide, molybdenum disulfide, bentones, carbon black, nitrobenzene, and the like. Generally, the amount of these modifiers is less than about percent of the total weight of the grease.

The subdivided polymers employed are preferably homopolymers of ethylene, homopolymers of propylene, and non-rubbery copolymers of ethylene and propylene. Mixtures of homopolymers and/or copolymers can also be employed. The ethylene polymers used in this invention are high density polymers, i.e., have a density at C. of at least 0.94 gram per cubic centimeter. The propylthe ASM grease in tackiness and consistency as well as in the characteristics shown in the table. However, best performance was obtained with the butadiene-styrene additive of the invention.

EXAMPLE II A butadiene-styrene copolymer having diiferent molecular weight and different butadiene-styrene ratios was added to ASM greases and evaluated as set forth in the table below. The grease employed contained 89.74 percent of a lubricating oil having a 500 SUS at 100 F. and an 80 V.I. index. The grease also contained 1 percent polyethylene, 6 percent methyl-Z-hydroxystearate, 2 percent hydrogenated castor oil, 1.2 percent lithium hydroxide, and 0.06 percent sodium hydroxide.

The results of these tests are set forth below in the table.

TABLE I.-.ASM GREASE WITH BUTADIENE-STYRENE POLYMER Butadlene-styrene polymer Penetrations Water Wheel Drop ASTM washbearing Per- 10,000 point, bleed, out, leakage, Ratio cent Unworked strokes strokes 2 F. F. percent percent gms.

Control 264 264 268 160 371 2. 78 3. 75 4. 0 000 41/59 1 260 265 268 158 429 1.43 2.50 4.30 /59 1 257 262 272 155 382 1. 0 0 3. 75 41/59 2 264 264 278 153 882 0 0 1. 8 41/59 3 267 297 305 160 374 0.23 2.50 11 4 41/59 1 252 256 257 391 38/62 1 260 254 270 393 0 1. 25 3. 35 75/25 1 260 256 272 381 0. 74 1. 25 3. 7

1 Indicated percentage of polymer replaces that of the lubricating 011.

one polymers can have a density at 25 C. of from 0.890 to 0.920 gram per cubic centimeter. The amount of subdivided polymer incorporated in the grease will generally be in the range of from about 0.1 to about 10, preferably from about 0.5 to about 5, weight percent based on the total weight of the greases.

Suitable grease compositions that can be employed according to the instant invention are defined in US. Pat. 3,432,431. However, it is within the scope of the invention to use other known greases thickened with other thickening agents as well.

The butadiene-styrene copolymer can be incorporated into the grease formulations by conventional blending machines as in grease manufacturing. These include stirred heating reactors, high speed blender: and milling machines.

EXAMPLE III A butadiene-styrene copolymer which had been hydrogenated and contained 41 percent butadiene and 59 percent styrene was added to a prelube and a Philube grease, and evaluated as in the previous examples.

TABLE IL-PRELUBE AND PHILUBE M.W. GREASES WITH BUTADIENE- STYRENE POLYMER Butadiene- Penetrations styrene Drop polymer, 60 10, 000 point, Ml. bleed Run percent 4 Unworked strokes strokes F. 94 hrs 1 Prelube 2 248 284 290 265 20. 2 Prelube 255 275 288 295 11.0 3 Phllube M.W. 2/18 275 385 5.0 4 Philube M.W. 247 265 283 398 3.0

; Slf mloer, average molecular weight oi polymer: 64,000

of lube stock of 3,900 SUS at 100 F. and 202 SUSat 210 F; 9% polyethylene.

0.04% rust inhibitor; and 1.0% 082.

4 Indicated percentage of polymer replaces that percentage of oil.

It will be noted from the above table that the addition of the butadiene-styrene copolymer substantially reduced the bleed characteristics of each of the greases tested and raised the drop point substantially.

In the above examples all of the butadiene-styrene copolymers employed as additives for the greases were hydrogenated prior to use. The hydrogenation was carried out so that less than about 10 percent of the original double bonds remained. Hydrogenation to about 5 percent or less residual unsaturation is fully acceptable.

The extent of hydrogenation of the olefinic bonds and of the phenyl groups in the butadiene-styrene copolymers can be determined by infrared analysis before and after hydrogenation.

I claim:

1. A grease composition improved as to bleeding, water wash-out and wheel bearing leaking properties consisting essentially of a thickened lubricating oil containing 0.5- weight percent of a hydrogenated rubbery butadiene-styrene copolymer having less than about 10 percent double bond unsaturation and having from 30- 75 weight percent butadiene and the remainder styrene and a molecular weight in the range l0,000-200,000.

2. A composition according to claim 1 wherein the thickened lubricating oil is an alkali metal soap grease.

3. A composition according to claim 1 wherein the amount of said butadiene-styrene copolymer is in the range 1-5 weight percent.

4. A composition according to claim 1 wherein said lubricating oil is an alkali metal soap grease containing 0.1-10 weight percent of polyolefin.

5. A composition according to claim 1 where the lubricating oil prior to being thickened is a mineral lubricating oil having an SUS at 210 F. in the range -250 and an SUS at 100 F. in the range SOD-5,000, and the thickened lubricating oil contains 0.1-10 weight percent of a particulate polyethylene.

6. A composition according to claim 1 wherein the lubricating oil composition is thickened with hydroxystearate, hydrogenated castor oil, and alkali metal hydroxide mixture.

7. A composition according to claim 6 which additionally contains polyethylene as a thickening agent, the amount of polyethylene present being in the range 0.1 to 10 Weight percent.

References Cited UNITED STATES PATENTS 3,432,431 3/1969 Mitacek 252--41 3,290,244 12/1966 Polishuk et a1. 252--41 2,274,749 3/1942 Smyers 252-59 3,630,905 12/1971 Sorgo 252-59 X CARL F. DEES, Primary Examiner US. Cl. X.R. 252-59 

